Alkamine esters of pyrrole-3, 4-dicarboxylic acids



Patented Nov. 9 1948 @ALKAMI-NE .E-sTERs F PYnRoLE-sA- DICARBOXYLIC ACIDS Jackson Px sickelsfflainfield, .L, :assignor to American Cyanamid Gomnamu New York,

:Y.,..-.a -.corporation..of iMaine.

No Drawing. ApplicatmnfNouember 1'3, 1946, SerialNo. 709,410 a l 11 Claims. (CL 1260-1313) This invention relatesto new alkamine esters of 1-aralkylpyrrole-BA-dioahboxylic acids.

The compounds of. the present invention may be represented by the following eneral formula:

or alkyLand Alkl and Alkz are residues ofldia'lkylamino alcohols.

The compounds of the present invention are ,not

intended to be limited to any particularmethod of production, but we have foundthat. it is'preferable to produce the-compounds .by catalyzed alcoholysis of the corresponding dialkyl .esters.

The pyrrole nucleus may be unsubstituted .onthe 2 and 5 carbon atoms. or there may bealkyl substituents. In general thealkyl esters areprepared by reacting thedialkyl ester ofa diketosuccinate with an aralkylamine under the standard conditionsfor this general.reactiondescribedbyjKnorr,

Berichte, vol. 18, page 299 et seq. The simplest .diketosuccinate is .the diacetosuccinate and this produces a l-aralky1-2,5-.diniethyl-.3;4dicarbalkoxypyrrole.

Other diketosuccinates may he use'd such as.

the dipropi-onosuccinate which will 'producefa 1-ara1kyl-2,5-diethyl 3,4-dicarbalkoxypyrrole.

The alcoholysis is preferably catalyze'dwith a small amount of an alkali metalflalcoholate.

Sodium is preferred because it is cheaper and while potassium gives equally good results its higher costis notlwarranted. The ialcoholysisreaction is not critical as to amounts of catalyst so long as they are below stoichiometric amounts.

Excellent results are obtained with an amount off alcoholate of the order of magnitude of stoichiometric equivalents. The alcoholysis is preferably carried out in the presence of an excess of the dialkylamino alcohol which is to be introduced. The alcoholate maybe introduced into the reaction mixture inupreformed .stateqor :theralkali metal may bedissolved inthe .aminoalcohol or added to the reaction mixture. .p'Iheimethod of introduction is notcritical, but we prefer'to-introduce the alcohola-te by dissolving the alkali-metal in the amino alcohol. Thesmoothness with which the aleoholysis reaction lDIGCBBdS is .snrprisingvin view of the ,known sensitiveness to oxidation in alkaline solution of amino alcohols and .their esters. No explanation .is advanced why :there- III 'boxyla'te is prepared by condensing benzylamine with diethyldiacetosuceinate in glacial: acetic acid eactirniiofthe pnesentinvention proceeds so readily sinwslllite10fstherlmownlsensitiveness of the react- ;antszand products to oxidation.

tithe .esters-lnlthe form of the free bases are for themost panttoilstboiling at high temperatures. They can betra-nsformed into salts of strong. min- -alacidsrsuchasihydrochlorides,by reaction with the anhydrous acid, preferably in solutionin an organic solvent such as ether. The hydrochlorides are fairly soluble in waterand permit use of some of the compounds .of the present invention as local anaesthetics. compounds also activate rubber vulcanization accelerators.

The invention will be described in greater detail in conjunction with the following specific examples in which the parts are by weight and the temperatures are uncorrected unless otherwise stated.

Example 1 Ditfidiethylaminoethyl) J benzyl-2,5-dimethylpyrrolaSA-dicarboxylate Diethyl-Lbenzyl Z,5-dimethylpyrrole 3,4 dicarsolution and 218 parts of the product aredisso'lved in 465 parts of fi-diethylamlnoethanol in which 2 parts of sodium have been dissolved. The reac-tionrmintureis heated fora longtperliod at C. and isthen-distilled'through a fractionating column provided with a large ratio of reflux, the first material lcomingover at 78 0., and the temperature gradually rising, until excess c-diethylaminoethanol begins to come on, whereupon the pressure is reduced anddistillation continued. A residual oil is obtained 'whichis distilled at about 2 mm. pressure, the boiling point being .between g l l-dhl c. The product obtained has ,a refiraetiveindexof about 1.53. Thesameoil is obtained b l /starting from dimethyl-l-benzyl-Qj- -.dimethylpyrrole -BAediearbOXyIate, the reaction pr-oceedingin-the-same manner but with aslightly :lower temperature in the reflux column, in .the .be-

-.ginnine. corresponding to the boiling pointof methyl alcohol.

Theadihydroch'loride may ;be prepared .by reactine the basic jester with dry hydrogench-lorideain etherysolution.

Example 2 Di ('y-diethylaminopropyl -1-benzyl-2,o-dlmetliylpyrrole- 3,4-dicarboxylate CoHaCH:

218 parts of diethyl-l-benzyl-2,5-dimethylpyrro1e-3, l-dicarboxy1ate are dissolved in about 500 parts of v-diethylaminopropanol in which about 2 parts of sodium have been dissolved. The reaction mixture is heated for a long period at 130-135 C. and is then distilled through a iractionating column with a high ratio of reflux. Ethyl alcohol set free in the reaction first distills off and then the temperature rises to the boiling point of the diethylaminopropanol, whereupon the pressure is reduced and the excess amino alcohol is distilled off under reduced pressure. The residue is dissolved in ether, washed with water and dried, and a high boiling oil is obtained which cannot be distilled under atmospheric pressure without decomposition.

Eacample 3 Di- (B-diethylamlnoethyl -1-methylbenzyl-2,5-dimetliylpyrrole-3,4-dicarboxylate =CC O O GH CHiN(CzH )2 CHaCtH4CH2N :0 0 O OCHzCHzN(CzH )i 230 parts of diethyl-1-methy1benzyl-2,5-dimethylpyrrole-3,4-dicarboxylate are prepared by condensation of a para-methylbenzylamine with diethyldiacetosuccinate in glacial acetic acid solution and 230 parts are dissolved in about 465 parts of fi-diethylaminoethanol in. which 2 parts of sodium have been dissolved.

The reaction mixture is then heated and distilled as described in the foregoing examples and the residue extracted With ether and Washed. A high boiling residual oil is obtained which does not distill at atmospheric pressure without decomposition.

Example 4 Di B-diethylaminoethyl) -1-phenylethyl-2,5-dimetl1ylpyrrole-3,4-dicarboxylate CH3 1 0 0 0 O CHzCHzN (C 2H5):

C H 0 H20 HzN 0:00 0 OCHCH2N(C2H5)2 Diethyl-1-phenylethyl-2,5-dimethylpyrrole-3,4- dicarboxylate is prepared by condensation. of B-phenylethylamine with diethyldiacetosuccinate in glacial acetic acid solution and 250 parts of'the product are dissolved in 480 parts of B-diethylaminoethanol in which about 2 parts of sodium have been dissolved. The reaction mixture is then heated and distilled as described in the foregoing examples, the residual oil extracted with ether and washed and dried. It does not distill at atmospheric pressure Without decomposition.

ethylaminopro-panol.

Example 5 Di (B-dlmethylaminoethyl) 1-benzyl-2,5-dimethylpyrrole-3,4-dicarboxylate =COOOCH2CH2N(CH3)2 CtH OHzN C: C O OCHaCHzN(CHa)z 'product of Example 1 and can not be distilled under atmospheric pressure without decomposition.

Example 6 Di ('y-dipropylaminopropyl) -1-benzyl-2,5-dlmethylpyrrole- 3,4-dicarboxylate The procedure of Example 2 is followed, substituting a stoichiometrically equivalent amount of dipropylaminopropanol for the 500 parts of y-di- A high boiling oil is obtained having properties similar to that of Example 2 and incapable of distillation under atmospheric pressure without decomposition.

This application is in part a continuation of my copending application Serial No. 496,964, filed July 31, 1943, now abandoned.

I claim:

1. A member of the group consisting of diesters of 'dialkylamino alkanols and l-aralkylpyrrole- '3,4-dicarboxylic acids and salts of the esters with strong mineral acids.

2. A member of the group consisting of diesters of; dialkylamino alkanols and l-aralkyl-2,5-

climethylpyrrole-3,4-dicarboxylic acids and salts of th'e'esters with strong mineral acids.

3. A member of the group consisting of diesters of dialkylamino alkanols and l-benzyl-2,5-dimethylpyrrole-3,4-dicarboxylic acids and salts of the esters with strong mineral acids.

4. Compounds according to claim 2 in which the alkylamino alcohol is fl-diethylaminoethanol.

5. A member of the group consisting of dimdiethylaminoethyl -1- benzyl-2, 5- dimethylpyrrole-3,4-dicarboxyl ate having the formula: 1

and their salts with strong acids.

6. A method of preparing a dialkamine ester of1-aralkylpyrrole-3-carboxylic acids which comprises subjecting'the diethyl ester of a l-aralkylpyrrole-3,4-dicarboxylic acid to alcoholysis with 'a dialkylamino alkanol in the presence of a catalytic amount of an alkali metal alcoholate.

7. A method of preparing a dialkamine ester of l-aralky1-2,5-dimethylpyrrole-3,4-dicarboxylic acid, which comprises subjecting the diethyl ester of the dicarboxylic acid to alcoholysis with a di- 9. A method according to claim 6 in which the alkylamino alkanol in the presence of a catalytic dialkylamino alkanol is fi-diethylaminoethanol. amount of an alkali metal alcoholate. 10. A method according to claim 7 in which the 8. A method of preparing a dialkamine ester dialkylamino alkanol is B-diethylaminoethanol. of 1-benzylpyrrole-3,4-dicarb0xy1io acids which 5 11. A method according to claim 8 in which the comprises subjecting the diethyl ester of a l-bendialkylamino alkanol is fi-diethylaminoethanol. zylpyrrole-3,4-dicarboxylic acid to alcoholysis JACKSON s1c s with a dialkylamino alkanol in the presence of a catalytic amount of an alkali metal alcoholate. No references cited. 

